This invention relates to the formation of a removable surface area of a certain depth on a substrate, along with all coatings, such as designs, glazings, sealants, protective coats and color coats, seated on the surface of the substrate. The invention also concerns a substrate reduced by a surface area of a certain depth, produced according to the proposed process.
It is frequently technically necessary or desirable to clean substrates on their surfaces and/or to free them of adhering coatings.
It is, in part, a very complicated and expensive necessity to separate the coating from the substrate, particularly if the substrate represents a valuable, reusable raw material, the properties of which are negatively altered by the adhering coatings in case of reuse of the substrate:
--In case the produced coating does not satisfy the technical requirements due to production errors, such as, for example, partial detachment, running of decorations, or the like,
--or in case the aesthetic impression deviates from the given standard, for example due to color changes.
Moreover, to an increasing extent, the manufacturer is forced by regulations and enacted laws to take his products back in the used state after they have served the customer.
In order to avoid paying additional costs for storage space, warehouse administration, and waste disposal, it is necessary to recycle these used products as "new" raw materials by incorporation into the respective manufacturing process. In this way, on the one hand, the expenses for storage of the returned, used products are considerably reduced and, on the other hand, expensive raw materials are, in part, saved by the recycling of these products.
However, frequently coatings or contaminations attached to the used product to be recycled must be removed since these prevent or decisively restrict the recycling of the basic material which otherwise would be technically feasible and advantageous.
Firmly entrenched coatings and/or contaminants, however, can be removed from the support in most cases only with very great expense and by complicated methods.
The state of the art is, for example:
--Mechanical grinding off or cutting off of the coatings, which takes a large amount of time, requires, in part, a great expenditure in costly machinery, grinding and separating agents, and moreover entails waste disposal problems in connection with the thus-produced fine dusts, coolants, and in wet processes the separation and concentration of the dust-containing suspensions.
--The burning off and oxidation of the coatings and/or contaminations with, in part, large amounts of emissions of possibly toxic gases, including a plurality of difficultly determinable organic and inorganic intermediates, in dependence on the temperature, the burner operation, and the atmosphere during the burning step.
Moreover, the energy costs to be expended in such processes are very high. Also, the furnace facilities and the flue gas and waste gas purification units which must be resistant to large amounts of fluxes, such as Pb.sup.2+, K.sup.+, Li.sup.+, Na.sup.+, etc., and corrosive gases containing F.sup.-, Cl.sup.-, are very expensive.
--Removal by caustics or etching with acids and/or bases. These processes are likewise complicated from an industrial viewpoint and expensive; moreover, the thus-formed reaction products can be disposed of as waste only with great difficulties.